1. Technical Field of the Invention
The present invention relates to a fan rotating blade for a turbofan engine.
2. Description of the Related Art
FIG. 1 is a schematic configuration diagram showing an aircraft engine 51 (a turbojet engine). As shown in this drawing, the turbojet engine is provided with a fan 52 for taking air thereinto, a compressor 53 for compressing the intake air, a combustor 54 for burning a fuel by the compressed air, a turbine 55 for driving the fan 52 and the compressor 53 by a combustion gas of the combustor 54, an after burner 56 for afterburning to increase a thrust, and the like.
In the invention, a pressure ratio indicates a total downstream pressure/a total upstream pressure of a blade. Additionally, a bypass ratio indicates a value obtained by dividing a flow rate on a bypass side (air directly passing through a nozzle to be discharged to the outside of the engine) by a flow rate on a core side (a flow toward the combustor via the compressor) at the downstream of the fan rotating blade.
The turbojet engine in which the fan 52 taking the air thereinto is enlarged in size and a bypass ratio is enlarged is called as “turbofan engine”. The bypass ratio corresponds to a flow rate ratio (bypass flow/core flow) between an air flow (a core flow) flowing into a core engine (the compressor 53, the combustor 54, and the turbine 55 described above) and a bypass flow bypassing them. There is obtained an effect of reducing a flow speed of an exhaust jet and lowering noise and fuel consumption, in accordance with an increase of the ratio.
However, in the above-described turbofan engine, a problem arises in that a fan first-stage rotating blade (an up-front fan) and an inner diameter of a casing surrounding the fan first-stage rotating blade are enlarged by enlarging the bypass ratio, and a weight of the engine is increased.
In order to solve the problem, there are already disclosed fan rotating blades having various shapes capable of increasing the flow rate of air introduced from the outside without increasing the inner diameter of the casing (Patent Documents 1 to 6: FIGS. 2A to 2F).
[Patent Document 1]
U.S. Pat. No. 6,328,533B1 “SWEPT BARREL AIRFOIL”
[Patent Document 2]
U.S. Pat. No. 6,071,077 “SWEPT FAN BLADE”
[Patent Document 3]
U.S. Pat. No. RE38040E “SWEPT TURBOMACHINERY BLADE”
[Patent Document 4]
U.S. Pat. No. 5,167,489 “FORWARD SWEPT ROTOR BLADE”
[Patent Document 5]
U.S. Pat. No. 5,725,354 “FORWARD SWEPT FAN BLADE”
[Patent Document 6]
U.S. Pat. No. 6,358,003 B2 “ROTOR BLADE AN AXIAL-FLOW ENGINE”
As described above, in the turbofan engine according to the conventional art, a problem arises in that the fan first-stage rotating blade (the up-front fan) and the inner diameter of the casing surrounding the fan first-stage rotating blade are enlarged by enlarging the bypass ratio, and the weight of the engine is increased.
Additionally, in the fan first-stage rotating blade according to the conventional art, for example, when a rotary speed is increased in order to increase an amount of air introduced from the outside, a circumferential speed increases too much, thereby causing a problem in that a loss of a shock wave excessively increases at a high flow rate.